Amxi°rnr;a^-rm*}  So-Called  Tasteless  Iron  Compounds.  175 
obtained,  containing  a  like  quantity  of  ammonio-ferric  pyrophosphate 
mixed  with  twice  as  much  ammonio-ferric  citrate  and  free  ferric  citrate 
as  the  officinal  salt  contains. 
The  writer  thinks  that  in  the  next  revision  of  the  Pharmacopoeia  the 
now  officinal  ammonio-pyrophosphate  should  be  dropped  and  replaced 
by  a  sodium  salt  represented  by  two  equivalents  of  ferric  citrate  and  one 
of  sodium  pyrophosphate  thus  : 
2(FeC6H50?)+Na4P207. 
Inverse  synthesis  can  not  exactly  produce  the  ammonio-citroferric 
orthophosphate  as  no  mixture  of  ferric  citrate  and  triammonic  phos- 
phate can  approach  any  nearer  than  equal  equivalents  of  each.  The 
writer,  however,  believes  that  also  in  this  case  a  sodium  compound  is 
better.  Ferric  citrate  and  disodic  phosphate  will  produce  perfectly 
green  compounds  in  proportions  that  do  not  exceed  4  equivalents  of 
the  former  to  one  of  the  latter. 
Ferric  orthophosphate  reacts  upon  triammonic  citrate  in  the  propor- 
tion of  two  equivalents  of  the  first  and  one  of  the  second,  producing 
a  solution  which  is  brown  red  by  transmitted  and  green  by  reflected 
light.  Addition  of  citric  acid,  monammonic  or  diammonic  citrate  to 
this  solution  discharges  the  red  color  mostly,  and  forms  a  solution 
which  is  also  green  by  transmitted  light.  By  evaporating  the  red  so- 
lution to  a  syrupy  consistence  and  spreading  it  on  plates  of  glass  or 
porcelain  beautiful  brownish  green  scales  are  easily  obtained.  Similar 
treatment  of  the  acidulated  solution  as  readily  yields  greenish  scales 
which  cannot  be  distinguished  by  appearance  from  the  officinal  pyro- 
phosphate. The  reddish  brown  color  of  this  compound  points  to  a 
basic  condition  due  to  the  presence  of  free  ferric  hydrate,  hence  its 
formation  may  be  written  thus  : 
4(FeP04)+2(NH1)3C6H607+3(OH2)=FeC6H507.(NH4)3C6H5Or+ 
2(FeP04).(NH4)3H3(P04)2+Fe(OH)3. 
This  result  assumes  the  generation  of  an  ammonio-ferric  orthophos- 
phate in  which  one  equivalent  each  monammonic  and  diammonic  phos- 
phate unite  to  form  a  neutral  phosphate  as  follows  : 
(NH4)2HP04+NH4H2P04=(NH4)3H3(P04)2. 
In  such  a  mixture  the  writer  attempted  to  dissolve  freshly  precipi- 
tated ferric  orthophosphate,  but  failed,  no  solution  taking  place.  How- 
ever a  trial  with  ferric  citrate  succeeded  perfectly,  and  a  new  salt  of  a 
brown-green  color  was  obtained.    Equal  equivalents  of  ferric  citrate 
